Control device for a marine drive unit

ABSTRACT

A control device for a marine drive unit, the device comprising a first mounting plate ( 10 ) for mounting said control device to a marine vessel, a second mounting plate ( 12 ) for mounting said control device to a marine drive unit, said first and second mounting plates ( 10, 12 ) being spatially separated and being communicably coupled by first and second pivotal mechanical links ( 20, 22 ) connected therebetween such that rotational movement of said mechanical links causes corresponding planar linear motion of said second mounting plate between a first, fully lowered position and a second, fully raised position, the control device further comprising a spring member ( 24 ) communicably coupled to said second mounting plate ( 12 ) and configured to exert an upward force thereon, said second mounting plate being configured, in use, to move toward said fully raised position in response to a further upward force applied thereto by thrust generated by said marine drive unit.

This invention relates to a control device for controlling the positionof a marine drive unit such as, for example, an outboard motor on aplaning boat.

Drive units for marine vehicles, such as power boats and the like, suchas outboard motors, are supported from the boat transom by a drivemounting assembly.

The drive mounting assembly for larger outboard motors often include apower tilt and trim device, which provides the ability to adjust thehull angle to match the water conditions and planing speeds. Boats withsmaller motors tend not to have a tilt and trim device fitted, but areinstead mounted such that they can be manually pivoted out of the wateror pivoted into the water as required, with the angle to the hullremaining fixed during use.

Transom extension mounting assemblies have become increasingly popular,particularly in high performance boats, where a lower position of themotor improves initial boat acceleration and a higher position enhancestop speed by reducing gear case drag.

Automatic control systems have been proposed, which include a sensor forsensing the speed of the boat, a control unit for determining a trimangle and/or vertical position of the motor which matches the sensedspeed of the boat (with a view to optimising the motor performance andoperation), and an electromechanical adjustment system which iscontrolled by the control unit and operable to automatically adjust thetrim angle and/or vertical position of the motor (relative to the boat)in response to control signals therefrom.

However, there are a number of problems associated with known suchcontrol systems. For example, they are relatively complex in nature and,therefore, tend to be expensive as well as prone to error. Furthermore,they require the provision of a separate power supply, which makes themunnecessarily bulky and increases the weight to be carried on the boatand also the space occupied therein. Finally, such systems need to betime-sensitive and immediately responsive, in real time, to changes inspeed and water conditions, if they are to operate effectively. On theother hand, the sensing and processing time taken to produce therequired control signals inevitably causes a time delay and reduces theresponsiveness of known systems in real time and, therefore, theireffectiveness in optimising motor performance and operation.

Aspects of the present invention seek to address at least some of theseproblems and exemplary embodiments of the present invention provide acontrol device for a marine drive unit, which aims to provide real timecontrol of at least the vertical position of the outboard motor, orsimilar marine drive unit, relative to the vessel on which it ismounted. Some exemplary embodiments additionally provide automatic trimcontrol without the need for driver or electronic input. Furthermore,embodiments of the present invention have the additional advantage ofbeing able to be retro-fitted to existing marine drive unit assemblies,which is often not possible with known control systems such as thosedescribed above.

In accordance with an aspect of the present invention, there is provideda control device for a marine drive unit, the device comprising a firstmounting plate for mounting said control device to a marine vessel, asecond mounting plate for mounting said control device to a marine driveunit, said first and second mounting plates being spatially separatedand being communicably coupled by first and second pivotal mechanicallinks connected therebetween such that rotational movement of saidmechanical links causes corresponding planar linear motion of saidsecond mounting plate between a first, fully lowered position and asecond, fully raised position, the control device further comprising aspring member communicably coupled to said second mounting plate andconfigured to exert an upward force thereon, said second mounting platebeing configured, in use, to move toward said fully raised position inresponse to a further upward force applied thereto by thrust generatedby said marine drive unit.

The spring member may comprise one or more torsion springs or torsionbars, such as helically wound torsion springs or torsion bars, coupledbetween the first mounting plate and at least one of the said first andsecond pivotal mechanical links. Alternatively, the spring member may beconnected diagonally between the first and second mounting plates,across the space therebetween.

In one exemplary embodiment, the spring member may be an extensionspring mounted diagonally between an upper end of the first fixing plateand a lower end of the second fixing plate. The first and second fixingplates may be substantially parallel to each other and the pivotalmechanical links may be arranged and configured therebetween to maintainsaid fixing plates substantially parallel to each other between saidfully lowered position and said fully raised position. In anotherexemplary embodiment of the invention, spring member is a compressionspring mounted diagonally between an upper end of the second fixingplate and a lower end of the first fixing plate. The pivotal mechanicallinks may be arranged and configured to cause the angle of the plane ofthe second fixing plate to change relative to the plane of the firstfixing plate as the second fixing plate moves from said fully loweredposition to said fully raised position.

The control device may further comprise at least one lower stop memberfor defining and limiting said fully lowered position and/or at leastone upper stop member for defining and limiting said fully raisedposition. In one exemplary embodiment, the at least one lower stopmember may comprise an elongate rod, the longitudinal axis of whichextends along the operational axis of the spring member, the rod havingan elongate longitudinal channel therein, wherein the rod iscommunicably coupled at the lower end of the second fixing plate bymeans of a pin provided thereon which is slideably received within saidchannel. Then at least one upper stop member may comprise a blockmounted on the inner surface of the first and/or second fixing plate.

In an exemplary embodiment, the angle of the plane of the second fixingplate relative to the plane of the first fixing device increases as thesecond fixing plate moves from said fully lowered position to said fullyraised position, so as to increase the hull angle of said marine driveunit relative to said marine vessel, in use.

The spring member may be provided with damping or dashpot means. Thebump and/or rebound settings of said damping or dashpot means may beselected to set the speed at which said second fixing plate movesbetween said fully raised position to said fully lowered position,and/or between said fully lowered position to said fully raised position

These and other aspects of the present invention will become apparentfrom the specific description given below, in which embodiments of theinvention are described, by way of examples only, and with reference tothe accompanying drawings, in which:

FIG. 1a is a schematic side view of a control device according to afirst exemplary embodiment of the present invention, illustrated in afully lowered configuration;

FIG. 1b is a schematic side view of the device of FIG. 1a , illustratedin a fully raised configuration;

FIG. 2a is a schematic side view of the device of FIG. 1a mountedbetween a boat transom and an outboard motor, and illustrated in thefully lowered configuration;

FIG. 2b is a schematic side view of the device of FIG. 1a mountedbetween a boat transom and an outboard motor, and illustrated in thefully raised configuration;

FIG. 3a is a schematic side view of a control device according to asecond exemplary embodiment of the present invention, illustrated in afully lowered configuration;

FIG. 3b is a schematic side view of the control device of FIG. 3a ,illustrated in a fully raised configuration;

FIG. 4 is a schematic side view of the device of FIG. 3a mounted betweena boat transom and an outboard motor, and illustrated in the fullylowered configuration;

FIG. 5a is a schematic side view of the device of FIG. 3a mountedbetween a boat transom and an outboard motor, and illustrated in thefully lowered configuration;

FIG. 5b is a schematic side view of the device of FIG. 3a mountedbetween a boat transom and an outboard motor, and illustrated in thefully raised configuration;

FIG. 6 is a schematic side view of the device of FIG. 3a mounted betweena boat transom and an outboard motor, and illustrated in the fullyraised configuration;

FIG. 7 is a schematic side view of a control device according to a thirdexemplary embodiment of the invention in the fully raised configuration;and

FIGS. 8 and 8 a are schematic side views of the control device of FIG. 7in the fully lowered configuration.

Referring to FIG. 1a of the drawings, a control device for a marinedrive unit according to a first exemplary embodiment of the presentinvention comprises a pair of substantially parallel fixing plates 10,12 formed of a strong, rigid material such as stainless steel or anon-ferrous metallic casting. It will be appreciated by a person skilledin the art that there are many different types of material suitable formarine applications, and which would be suitable for forming the fixingplates 10, 12, and the present invention is not intended to be limitedin this regard.

The first fixing plate 10 is configured to be mounted to the transom ofa boat in any suitable manner, for example, by means of nut and boltassemblies (14, FIG. 2a ) provided at suitable locations between thetransom (30, FIG. 2a ) and the plate 10. It will be appreciated by aperson skilled in the art that different methods of fixing a metallicplate or structure to a boat transom are known, and the presentinvention is not necessarily intended to be limited in this regard.

The second fixing plate 12 is configured to be mounted to the mountingbracket of an outboard motor, or other marine drive unit, and may be ofsimilar construction to the first fixing plate 10, although it maydiffer slightly in length, according to the dimensions of the drive unitmounting bracket to which it is required to be fixed. Once again,various suitable methods for fixing the second fixing plate 12 to themounting bracket (16, FIG. 2a ) of a marine drive unit (18, FIG. 2a )will be apparent to a person skilled in the art. For example, nut andbolt assemblies between the plate 12 and the mounting bracket (16, FIG.2a ) may be used, but other fixing methods are envisaged, and thepresent invention is not necessarily intended to be limited in thisregard.

Furthermore, conventional engine mounting mechanisms are known formounting a drive unit to a boat, which allow the static vertical heightof the engine relative to the boat to be selected and fixed duringmounting, and it is envisaged that this facility may also be providedvia the first and/or second fixing plate, for example, by providingseveral sets of mounting holes at different longitudinal positionsthereon.

A first pair of hinged links 20 (one shown in FIG. 1a ) pivotallyconnect the first and second fixing plates 10, 12 between the upper endof the second fixing plate 12 and a point below the upper end of thefirst fixing plate 10. The hinged links 20 are provided on opposing sideedges of the first and second fixing plates 10, 12 such that only onecan be seen in the side view illustrated in FIG. 1a of the drawings.

A second pair of hinged links 22 (one shown in FIG. 1a ) pivotallyconnect the first and second fixing plates 10, 12 between the lower endof the first fixing plate 10 and a point above the lower end of thesecond fixing plate 12. The exact positions on the fixing plates 10, 12of the first and second hinged links 20, 22 are dependent on thedimensions of the plates 10, 12, amongst other things, and the presentinvention is not necessarily intended to be limited in this regard.However, it is clear from FIG. 1a , that their relative connectingpositions on the fixing plates 10, 12 are such that the first hingedlinks 20 are substantially longitudinally parallel to the second hingedlinks 22 in this exemplary embodiment of the present invention suchthat, in use, the links 20, 22 operate in a cam-like fashion in thesense that planar linear movement of the second fixing plate 12 relativeto the first fixing plate 10 causes corresponding rotational movement ofthe links 20, 22, and vice versa.

An elongate tension spring 24 is pivotally mounted between the upper endof the first fixing plate 10 and a point at or close to the lower end ofthe second fixing plate 12, such that it extends diagonally across thespace defined between the two ends of the plates 10,12. In one exemplaryembodiment of the present invention, the spring 24 may comprise a gasspring. In an alternative exemplary embodiment, the spring 24 maycomprise a helically wound spring, having a generally central,longitudinal axis. Other tension spring mechanisms are known, and thepresent invention is not necessarily intended to be limited in thisregard.

Irrespective of the nature of the spring 24, it may be damped in a knownmanner, or known damping or dashpot means may be provided separatelytherefrom to provide the damping required according to the devicespecification.

A pair of elongate pivotal stop plates 24 a extend diagonally across thespace between the fixing plates 10, 12, and are pivotally mounted atsubstantially the same positions as the spring 24, at the upper end ofthe first fixing plate 10 and at or close to the lower end of the secondfixing plate 12, such that the stop plates 24 a extend alongside andparallel to the length of the spring 24, with the stop plates 24 a beinglocated on opposing sides thereof such that only one can be seen in theview illustrated in FIG. 1 a.

The lower end of each stop plate 24 a is provided with a longitudinalchannel 28 in which a pin 26, provided on the second fixing plate 12, isslideably received. These channels 28 effectively provide lower stops todefine and limit the maximum downward travel of the device componentsrelative to each other, according to device specifications. Furthermore,stops (not shown) may be provided on the inner surface of the firstand/or second fixing plate to define and limit the maximum upward travelof the device components relative to each other, according to devicespecifications.

In use, and referring additionally to FIGS. 1b, 2a and 2b of thedrawings, the first fixing plate 10 is mounted to the transom 30 of aboat using the mounting points provided thereon for mounting an outboardmotor. The second fixing plate 12 is mounted to the mounting bracket 16of an outboard motor 18 (or other marine drive unit), once again usingthe mounting points provided thereon for mounting the motor 18 to theboat transom 30.

When the boat is at rest (or travelling very slowly), the control deviceholds the motor 18 in a “fully lowered position” at a predeterminedmaximum depth relative to the boat due to the weight of the motor 18causing the pin 26 on the second fixing plate 12 to exert a downwardforce against the lower end of the channel 28. In this position, thetension spring 24 exerts an upward force on the second fixing plate 12and, therefore, the motor 18, due to the stored energy therein, but thisupward force on its own is insufficient to counteract the downward forceacting on the stop plates 24 a via the respective pins 26 in thechannels 28. As the throttle is opened, the thrust of the motorpropeller acts to exert an additional upward force on the second fixingplate 12 and motor 18, which upward force acts together with the upwardforce exerted by the spring 24 to counteract the weight of the motor 18and raise the second fixing plate 12 and motor out of the water. As thesecond fixing plate 12 moves upward, The speed at which the motor 18 israised is dependent on the so-called “bump” setting of the damper ordashpot associated with the spring 24 (4 or 5 seconds is typical for aboat to get on the plane, but the present invention is not intended tobe limited in this regard). As the second fixing plate 12 rises, the pin26 slides along the channel 28 until it reaches the top, at which point,further movement of the second fixing plate 12 upward causes the spring24 and the second fixing plate 12 to pivot toward the first fixing plate10, until the fully raised position illustrated in FIGS. 1b and 2b isreached. The fully raised position is determined by the upper stops (notshown) which may be provided on the inner surface of the first and/orsecond fixing plate such that they prevent further movement of thesecond fixing plate toward the first fixing plate. However, it will beappreciated that, until the fully raised position is reached, the heightof the second fixing plate 12 and, therefore, the motor 18 relative tothe boat transom 30 is purely a function of propeller thrust generated.

When little or no propeller thrust is present (i.e. does not produceenough upward force to counteract, in conjunction with the spring 24,the weight of the motor 18), the weight of the outboard motor causes thesecond fixing plate to drop down once again, such that the pin slidesdown the channel 28 to the bottom. Once again, the length andconfiguration of the channels 28 in the stop plates 24 a dictate thelevel to which the second fixing plate 12 can drop, i.e. the “fullylowered position” illustrated in FIGS. 1a and 2a . The speed at whichthe engine is thus lowered is dependent on the “rebound” setting of thedamper or dashpot associated with the spring 24.

The exemplary embodiment described above with reference to FIGS. 1 and 2of the drawings is primarily intended for use with a marine vehicle,such as a planing hull, fitted with an outboard motor over around 50 HPwith a power tilt and/or trim device fitted. Thus, in use, the controldevice enables the motor to be automatically raised and lowered,according to the thrust of the motor propeller, without activelychanging the trim angle, i.e. the trim angle (as set by the power trimdevice) is maintained during operation of this exemplary embodiment ofthe present invention.

The described embodiment may improve speed, acceleration and fuelconsumption automatically, without driver input, by:

-   -   Lifting the engine higher out of the water at higher speeds,        thereby reducing hydrodynamic drag, and thus increasing speed        and lowering fuel consumption;    -   Lowering the engine further into the water at low speeds, thus        reducing the risk of propeller ventilation and poor propeller        thrust during acceleration.

Referring to FIGS. 3a and 3b of the drawings, a control device for amarine drive unit according to a second exemplary embodiment of thepresent invention is primarily intended for engines not fitted with apower trim and/or tilt device, and can have its link points and pivotsconfigured such that, as the engine rises out of the water, the assemblyactively changes the angle between the engine and the boat, thereby“trimming the engine out”. The illustrated device comprises a pair offixing plates 10 a, 12 a formed of, for example, stainless steel orother rigid material suitable for use in marine applications.

Referring additionally to FIGS. 4, 5 a, 5 b and 6 of the drawings, onceagain, the first fixing plate 10 a is configured to be mounted to thetransom 30 of a boat in any suitable manner, and the second fixing plate12 a is configured to be mounted to the mounting bracket 16 of anoutboard motor 18 or other marine drive unit in any suitable manner.Furthermore, it is once again envisaged that the mounting means mayprovide several possible (static) heights and/or several possible(static)) trims at which the motor can be mounted, as required.

A first pair of hinged links 20 a (one shown in FIGS. 3a and 3b )pivotally connect the first and second plates 10 a, 12 a between theupper end of the second fixing plate 12 a and a position below the upperend of the first fixing plate 10 a. The hinged links 20 a are providedat opposing side edges of the plates 10 a, 12 a, thus, only one can beseen in the side views of FIGS. 3a and 3 b.

A second pair of hinged links 22 a (one shown in FIGS. 3a and 3b )pivotally connect the first and second fixing plates 10 a, 12 a betweenthe lower end of the first fixing plate 10 a and a position above thelower end of the second fixing plate 12 a. Once again, the exactpositions on the plates 10 a, 12 a of the first and second hinged links20 a, 22 a are dependent on the dimensions of the plates 10 a, 12 a,amongst other things, and the present invention is not necessarilyintended to be limited in this regard. However, it is clear from FIGS.3a and 3b that the hinged links are configured to enable the secondfixing plate 12 a to pivot between a first position (shown in FIG. 3a )in which it is angled toward the first fixing plate 10 a, to a secondposition (shown in FIG. 3b ) in which it is substantially vertical whenthe control device is in use and mounted to a boat transom. Once again,the hinged links 20 a, 22 a are also configured to operate in a cam-likefashion in the sense that linear planar movement of the second fixingplate 12 a causes corresponding rotational movement thereof, and viceversa.

An elongate gas, helically wound or other mechanical compression spring25, which may be damped or have one or more separate dampers or dashpotsassociated therewith, is mounted between the upper end of the secondfixing plate 12 a and the lower end of the first fixing plate 10 a, suchthat it extends diagonally across the space between the two ends of thefixing plates 10 a, 12 a.

A first end of the spring 25 is pivotally mounted at the upper end ofthe second fixing plate 12 a. The opposite end of the spring 25 ispivotally mounted at a fixed point at the lower end of the first fixingplate 10 a. It is envisaged, but not shown in FIGS. 3a and 3b of thedrawings, that this embodiment may include lower stop means, fordefining and limiting the maximum downward travel of the devicecomponents relative to each other, according to device specifications.Such lower stop means may again comprise a pair of elongate pivotal stopplates, pivotally mounted alongside and parallel to the spring 25, witha pin and channel arrangement such as that described with reference toFIGS. 1a and 1b of the drawings. However, other lower stop means arealso envisaged.

In use, the first fixing plate 10 a is mounted to the transom 30 of aboat using the mounting points provided thereon for mounting an outboardmotor. The second fixing plate 12 a is mounted to the mounting bracket16 of an outboard motor 18 (or other marine drive unit), once againusing the mounting points provided thereon for mounting the motor to theboat transom.

The second exemplary embodiment is particularly, but not necessarilyexclusively, suited for use with planing hulls or marine vessels fittedwith an outboard motor (or other marine drive unit) up to approximately50 HP, which is not fitted with a power trim device, and is intended toimprove safety, speed and fuel consumption automatically, with no driverinput, in the manner described above.

Both of the exemplary embodiments described above have the additionaladvantage of providing a degree of “setback”. Setback is the distancebetween the outboard motor bracket and the boat transom. When the engineis mounted directly to the transom, there is said to be zero setback,but increasing the setback helps maintain a smoother flow of water fromthe bottom of the transom into the path of the propeller, and this isprovided by exemplary embodiments of the invention.

Referring to FIGS. 7 and 8 of the drawings, a control device for amarine drive unit according to a third exemplary embodiment of thepresent invention once again comprises a pair of fixing plates 10 a, 12a, wherein the first fixing plate 10 a is configured to be mounted tothe transom 30 of a boat in any suitable manner, and the second fixingplate 12 a is configured to be mounted to the mounting bracket 16 of anoutboard motor 18 or other marine drive unit in any suitable manner.

A first pair of hinged links 20 a pivotally connect the first and secondplates 10 a, 12 a between a position below the upper end of the secondfixing plate 12 a and the upper end of the first fixing plate 10 a; anda second pair of hinged links 22 a pivotally connect the first andsecond fixing plates 10 a, 12 a between the respective lower endsthereof. As before, however, the exact positions on the plates 10 a, 12a of the first and second hinged links 20 a, 22 a are dependent on thedimensions of the plates 10 a, 12 a amongst other things, and thepresent invention is not necessarily intended to be limited in thisregard.

A helically wound torsion spring or torsion bar 140 is provided as thepivotal connection between the second hinged link(s) 22 and the firstfixing plate 10 a, and acts therebetween. The torsion spring(s) orbar(s) are located axially over the respective pivot pins 22 bconnecting the first fixing plate 10 a to the second hinged links.Alternatively, a torsion bar could be used as the aforementioned pivotpin fixed at one end to the first fixing plate 10 a and at its other endto the respective second hinged link 22 a.

When the boat is at rest (or travelling very slowly), the control deviceholds the motor 18 in a “fully lowered position” at a predeterminedmaximum depth relative to the boat, as shown in FIG. 7 of the drawings,to reduce the risk of propeller ventilation and poor propeller thrustduring acceleration, and the angle of the second fixing plate 12 a atthis stage is such that the bow of the boat is fully or partly trimmeddown, thereby ensuring that the driver has good forward vision andstability. The second fixing plate 12 a remains in this position, whenthere is little or no propeller thrust, due to the weight of the motor18 exerting a downward force on the lower stops (not shown). In thisposition, the torsion spring 140 exerts an upward force on the secondfixing plate 12 a, via the second hinged link 22 a, and, therefore, themotor, due to the stored energy therein, but this upward force on itsown is insufficient to counteract the downward force acting on the lowerstops. As the throttle is opened, the thrust of the motor propeller actsto exert an additional upward force on the second fixing plate 12 a andmotor 18, which upward force acts together with the upward force exertedby the torsion spring 140 to counteract the weight of the motor andraise the second fixing plate 12 a and motor out of the water. As thesecond fixing plate 12 rises, the hinged links 20 a, 22 a pivot in ananticlockwise direction, to cause corresponding upward and asymmetricpivotal movement of the second fixing plate 12 a [i.e. by a greaterdegree about the upper pivotal connection than about the lower pivotalconnection (if any)] to the fully raised position illustrated in FIGS. 8and 8 a, in which the second fixing plate is substantially vertical,thereby lifting the outboard motor and also trimming up the bow toincrease speed, reduce hydrodynamic drag and reduce fuel consumption athigher speeds. Once the boat slows down sufficiently, or stops, theweight of the motor 18 once again causes the second fixing plate 12 a todrop down and return to the fully lowered position illustrated in FIG.7. Once again, the distance to which the second fixing plate 12 a and,therefore, the motor can be raised and lowered is dependent on upper andlower stops (not shown). It will be appreciated that, until the fullyraised position is reached, the height of the second fixing plate 12 aand, therefore, the motor relative to the boat transom 30 is purely afunction of propeller thrust generated.

It will be appreciated that the present invention is very different to aknown hydraulic or manual jackplate. For example, a hydraulic jackplaterequires a power source, a motor, a hydraulic pump and a hydraulic ram.In addition, with such known devices, constant driver input is requiredto maintain optimum engine height by either raising or lowering thehydraulic ram with electrical controls at the helm. This is true, evenif such electrical controls are generated by a central control unit.Furthermore, known manual jackplates must be set at a specific,compromised height before the boat is used, and cannot be adjustedwhilst the boat is in motion. Thus, in addition to the above-mentionedadvantages, exemplary embodiments of the present invention providefurther advantageous features over known systems.

It will be apparent to a person skilled in the art from the foregoingdescription that modifications and variations can be made to thedescribed embodiments without departing from the scope of the inventionas claimed. For example, the extension spring configuration illustratedand described with respect to FIGS. 1 a, 1 b, 2 a and 2 b may beemployed to realise a variable trim arrangement such as that describedwith reference to FIGS. 3a and 3b , and vice versa.

1. A control device for a marine drive unit, the device comprising afirst mounting plate for mounting said control device to a marinevessel, a second mounting plate for mounting said control device to amarine drive unit, said first and second mounting plates being spatiallyseparated and being communicably coupled by first and second pivotalmechanical links connected therebetween such that rotational movement ofsaid mechanical links causes corresponding planar linear motion of saidsecond mounting plate between a first, fully lowered position and asecond, fully raised position, the control device further comprising aspring member communicably coupled to said second mounting plate andconfigured to exert an upward force thereon, said second mounting platebeing configured, in use, to move toward said fully raised position inresponse to a further upward force applied thereto by thrust generatedby said marine drive unit.
 2. The control device of claim 1, whereinsaid spring member comprises one or more torsion springs or torsion barscoupled between said first mounting plate and at least one of said firstand second pivotal mechanical links.
 3. The control device of claim 2,wherein said spring member comprises one or more helically wound torsionsprings or torsion bars.
 4. The control device of claim 1, wherein saidspring member is connected diagonally between said first and secondmounting plates across the space therebetween.
 5. The control device ofclaim 1, further comprising at least one lower stop member for definingand limiting said fully lowered position.
 6. The control device of claim1, further comprising at least one upper stop member for defining andlimiting said fully raised position.
 7. The control device of claim 5,wherein said at least one lower stop member comprises an elongate rod,the longitudinal axis of which extends along the operational axis of thespring member, the rod having an elongate longitudinal channel therein,wherein the rod is communicably coupled at the lower end of the secondfixing plate by means of a pin provided thereon which is slideablyreceived within said channel.
 8. The control device of claim 6, whereinsaid at least one upper stop member comprises a block mounted on theinner surface of the first and/or second fixing plate.
 9. The controldevice of claim 1, wherein said spring member is an extension springmounted diagonally between an upper end of the first fixing plate and alower end of the second fixing plate.
 10. The control device of claim 1,wherein the first and second fixing plates are substantially parallel toeach other and the pivotal mechanical links are arranged and configuredtherebetween to maintain said fixing plates substantially parallel toeach other between said fully lowered position and said fully raisedposition.
 11. The control device of claim 1, wherein said spring memberis a compression spring mounted diagonally between an upper end of thesecond fixing plate and a lower end of the first fixing plate.
 12. Thecontrol device of claim 1, wherein said pivotal mechanical links arearranged and configured to cause the angle of the plane of the secondfixing plate to change relative to the plane of the first fixing plateas the second fixing plate moves from said fully lowered position tosaid fully raised position.
 13. The control device of claim 12, whereinsaid angle of the plane of the second fixing plate relative to the planeof the first fixing device increases as the second fixing plate movesfrom said fully lowered position to said fully raised position, so as toincrease the hull angle of said marine drive unit relative to saidmarine vessel, in use.
 14. The control device of claim 1, wherein saidspring member is provided with damping or dashpot means.
 15. The controldevice of claim 14, wherein the bump and/or rebound settings of saiddamping or dashpot means are selected to set the speed at which saidsecond fixing plate moves between said fully raised position to saidfully lowered position, and/or between said fully lowered position tosaid fully raised position.
 16. (canceled)
 17. The control device ofclaim 1, further comprising at least one lower stop member for definingand limiting said fully lowered position.